سنن النسائي

It was narrated from 'Ubdah bin As-Samit-who had been present at Badar and had given his pledge to the Prophet (ﷺ) swearing not to fear the blame of any blamer for the sake of Allah that 'Ubadah stood up to deliver a speech and said: "O people, you have invented kinds of transactions, I do not know what they are, but make sure it is gold for gold, of the same weight, or silver for silver, of the same weight. There is nothing wrong with selling silver for gold, hand to hand, giving more silver than gold, but no credit is allowed. When you sell wheat for wheat and barley for barley, it should be measure for measure, but there is nothing wrong with selling barley for wheat, hand to hand, giving more barley than wheat, but no credit is allowed. And when you sell dates for dates, it should be measure for measure" And he mentioned salt, "measure for measure, and whoever gives more or asks for more has engaged in Riba.